Protein for blocking platelet adhesion

Abstract

A naturally occurring protein isolated from the saliva of the medicinal leech Hirudo medicinalis is described which strongly binds to collagen thus acting as an inhibitor of natural platelet adhesion to collagen. The protein has a molecular weight of about 12,000, an acidic isoelectric point and contains six cysteins. The protein was sequenced and the gene was cloned from a H. medicinalis cDNA-library. Procedures for producing such polypeptide by recombinant techniques are disclosed. The recombinant and the natural occurring proteins are potent inhibitors of collagen-dependent platelet adhesion and therefore useful for the therapeutic treatment of various conditions related to heart disease and diseases of the circulation system. Furthermore, the protein is useful for coating natural or artificial collagen surfaces in order to render them nonadhesive for cells and prevent the activation of cells.

1. A method of identifying compounds that compete with the binding of Saratin to collagen, comprising:
 determining the binding of said Saratin to collagen in the presence or absence of a competitor. 
 
     
     
       2. The method of  claim 1  wherein said Saratin is the same as a polypeptide isolated from  Hirudo medicinalis  and has a molecular weight of about 12,000±1 kD. 
     
     
       3. The method of  claim 1 , wherein said Saratin is biotinylated Saratin. 
     
     
       4. The method of  claim 1 , wherein said Saratin comprises the amino acid sequence set forth in SEQ ID NO:2. 
     
     
       5. The method of  claim 1 , wherein said competitor is an antibody. 
     
     
       6. The method of  claim 1 , wherein said competitor is a blocking anti-Saratin antibody.